This invention relates generally to devices for interventional therapeutic treatment or vascular surgery for treatment of defects in the vasculature, and more particularly concerns an expansion ring for opening ends of a braided stent for treatment of vascular disease.
Stents, which are tubular reinforcements inserted into a blood vessel to provide an open path within the blood vessel, have been widely used in intravascular angioplasty treatment of occluded cardiac arteries. In such applications, the stent is inserted after an angioplasty procedure or the like in order to prevent restenosis of the artery. In these applications, the stents are often deployed by use of inflatable balloons, or mechanical devices which force the stent open, thereby reinforcing the artery wall and provide a clear through-path in the center of the artery after the angioplasty procedure to prevent restenosis.
While such procedures may be useful in certain aspects of vascular surgery in which vasoocclusive devices are used, the weakness of the vasculature and the tortuosity of the neurovasculature places limits on the applicability of such stents in procedures to repair neurovascular defects. Furthermore, the use of placement techniques, such as balloons or mechanical expansions of the type often found to be useful in cardiac surgery, are relatively less useful in vasoocclusive surgery, particularly when tiny vessels, such as those found in the brain, are to be treated. Hence, those skilled in the art have recognized a need for a stent compatible with techniques in vasoocclusive treatment of neurovascular defects that provides selective reinforcement in the vicinity of a neurovascular defect, while avoiding any unnecessary trauma or risk of rupture to the blood vessel.
Braided stents are typically formed from a plurality of elongate members, such as two or more metal wires, or polymeric fibers or strands of material, for example, and can be very useful in treatment of neurovascular defects. However, one of the problems in deploying a self-expanding braided stent in a body lumen is activation of the initially expanding end, typically the distal end of the braided stent, to fully open. It is important that the initially expanding end should open fully, easily, and quickly, so that the rest of the length of self-expanding braided stent can be deployed, using the initially expanding end as an anchor point.
Stents made of braided wire also commonly have a high internal friction that resists the inherent radial expansion force of the self-expanding braided stent to open, particularly resisting opening of the initially expanding end, which can cause problems in anchoring and deployment of such self-expanding braided stents. Current self-expanding braided stents are commonly not optimal because they depend solely on their material, dimension, cell design, and internal friction to expand. Deployment of such self-expanding braided stents commonly require extra manipulation by a user to fully open the self-expanding braided stents, which affects placement accuracy and adds risk to the procedure. The deployment and fixation of the distal end of a self-expanding braided stent is necessary for the proper alignment and positioning of the remainder of the stent body.
It would be desirable to provide an expansion ring that can be attached to an end of a braided stent to insure that the braided stent will fully expand during delivery of the braided stent to a treatment site once the braided stent is unconstrained by a delivery microcatheter. It would be desirable to provide an expansion ring with a design that simplifies the attachment of the expansion ring to a braided stent. The present invention meets these and other needs.